/**
 * IK 中文分词  版本 5.0
 * IK Analyzer release 5.0
 * 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * 源代码由林良益(linliangyi2005@gmail.com)提供
 * 版权声明 2012，乌龙茶工作室
 * provided by Linliangyi and copyright 2012 by Oolong studio
 * 
 */
package org.wltea.analyzer.query;

import java.io.IOException;  
import java.io.StringReader;  
import java.util.ArrayList;  
import java.util.List;  
  
import org.apache.lucene.analysis.standard.StandardAnalyzer;  
import org.apache.lucene.queryparser.classic.ParseException;  
import org.apache.lucene.queryparser.classic.QueryParser;  
import org.apache.lucene.search.Query;  
import org.wltea.analyzer.core.IKSegmenter;  
import org.wltea.analyzer.core.Lexeme;  
  
/** 
 * Single Word Multi Char Query Builder 
 * IK分词算法专用  暴走抹茶 2017.3.28 
 * @author linliangyi 
 * 
 */  
public class SWMCQueryBuilder {  
  
    /** 
     * 生成SWMCQuery 
     * @param fieldName 
     * @param keywords 
     * @param quickMode 
     * @return Lucene Query 
     */  
    public static Query create(String fieldName ,String keywords , boolean quickMode){  
        if(fieldName == null || keywords == null){  
            throw new IllegalArgumentException("参数 fieldName 、 keywords 不能为null.");  
        }  
        //1.对keywords进行分词处理  
        List<Lexeme> lexemes = doAnalyze(keywords);  
        //2.根据分词结果，生成SWMCQuery  
        Query _SWMCQuery = getSWMCQuery(fieldName , lexemes , quickMode);  
        return _SWMCQuery;  
    }  
      
    /** 
     * 分词切分，并返回结链表 
     * @param keywords 
     * @return 
     */  
    private static List<Lexeme> doAnalyze(String keywords){  
        List<Lexeme> lexemes = new ArrayList<Lexeme>();  
        IKSegmenter ikSeg = new IKSegmenter(new StringReader(keywords) , true);  
        try{  
            Lexeme l = null;  
            while( (l = ikSeg.next()) != null){  
                lexemes.add(l);  
            }  
        }catch(IOException e){  
            e.printStackTrace();  
        }  
        return lexemes;  
    }  
      
      
    /** 
     * 根据分词结果生成SWMC搜索 
     * @param fieldName 
     * @param pathOption 
     * @param quickMode 
     * @return 
     */  
    private static Query getSWMCQuery(String fieldName , List<Lexeme> lexemes , boolean quickMode){  
        //构造SWMC的查询表达式  
        StringBuffer keywordBuffer = new StringBuffer();  
        //精简的SWMC的查询表达式  
        StringBuffer keywordBuffer_Short = new StringBuffer();  
        //记录最后词元长度  
        int lastLexemeLength = 0;  
        //记录最后词元结束位置  
        int lastLexemeEnd = -1;  
          
        int shortCount = 0;  
        int totalCount = 0;  
        for(Lexeme l : lexemes){  
            totalCount += l.getLength();  
            //精简表达式  
            if(l.getLength() > 1){  
                keywordBuffer_Short.append(' ').append(l.getLexemeText());  
                shortCount += l.getLength();  
            }  
              
            if(lastLexemeLength == 0){  
                keywordBuffer.append(l.getLexemeText());                  
            }else if(lastLexemeLength == 1 && l.getLength() == 1  
                    && lastLexemeEnd == l.getBeginPosition()){//单字位置相邻，长度为一，合并)  
                keywordBuffer.append(l.getLexemeText());  
            }else{  
                keywordBuffer.append(' ').append(l.getLexemeText());  
                  
            }  
            lastLexemeLength = l.getLength();  
            lastLexemeEnd = l.getEndPosition();  
        }  
  
        //借助lucene queryparser 生成SWMC Query  
        QueryParser qp = new QueryParser(fieldName, new StandardAnalyzer());  
        qp.setDefaultOperator(QueryParser.AND_OPERATOR);  
        qp.setAutoGeneratePhraseQueries(true);  
          
        if(quickMode && (shortCount * 1.0f / totalCount) > 0.5f){  
            try {  
                //System.out.println(keywordBuffer.toString());  
                Query q = qp.parse(keywordBuffer_Short.toString());  
                return q;  
            } catch (ParseException e) {  
                e.printStackTrace();  
            }  
              
        }else{  
            if(keywordBuffer.length() > 0){  
                try {  
                    //System.out.println(keywordBuffer.toString());  
                    Query q = qp.parse(keywordBuffer.toString());  
                    return q;  
                } catch (ParseException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
        return null;  
    }  
}  
